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Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up

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ABSTRACT

Background: Cancer makes up a large and increasing proportion of excess mortality for indigenous, marginalised and socioeconomically deprived populations, and much of this inequality is preventable. This study aimed to determine which cancers give rise to changing ethnic inequalities over time.

Methods: New Zealand census data from 1981, 1986, 1991, 1996, 2001, and 2006, were all probabilistically linked to three to five subsequent years of mortality (68 million person-years) and cancer registrations (87 million person years) and weighted for linkage bias. Age-standardised rate differences (SRDs) for Māori (indigenous) and Pacific peoples, each compared to European/Other, were decomposed by cancer type.

Results: The absolute size and percentage of the cancer contribution to excess mortality increased from 1981–86 to 2006–11 in Māori males (SRD 72.5 to 102.0 per 100,000) and females (SRD 72.2 to 109.4), and Pacific females (SRD −9.8 to 42.2) each compared to European/Other.

Results: Specifically, excess mortality (SRDs) increased for breast cancer in Māori females (linear trend p < 0.01) and prostate (p < 0.01) and colorectal cancers (p < 0.01) in Māori males. The incidence gap (SRDs) increased for breast (Māori and Pacific females p < 0.01), endometrial (Pacific females p < 0.01) and liver cancers (Māori males p = 0.04), and for cervical cancer it decreased (Māori females p = 0.03). The colorectal cancer incidence gap which formerly favoured Māori, decreased for Māori males and females (p < 0.01).

Results: The greatest contributors to absolute inequalities (SRDs) in mortality in 2006–11 were lung cancer (Māori males 50 %, Māori females 44 %, Pacific males 81 %), breast cancer (Māori females 18 %, Pacific females 23 %) and stomach cancers (Māori males 9 %, Pacific males 16 %, Pacific females 20 %). The top contributors to the ethnic gap in cancer incidence were lung, breast, stomach, endometrial and liver cancer.

Conclusions: A transition is occurring in what diseases contribute to inequalities. The increasing excess incidence and mortality rates in several obesity- and health care access-related cancers provide a sentinel warning of the emerging drivers of ethnic inequalities. Action to further address inequalities in cancer burden needs to be multi-pronged with attention to enhanced control of tobacco, obesity, and carcinogenic infectious agents, and focus on addressing access to effective screening and quality health care.

Electronic supplementary material: The online version of this article (doi:10.1186/s12885-016-2781-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


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Decomposition of absolute ethnic inequalities in cancer incidence by major contributing cancer types, comparing Māori and Pacific with European/Other in males and females aged 1–74 years in New Zealand
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Fig5: Decomposition of absolute ethnic inequalities in cancer incidence by major contributing cancer types, comparing Māori and Pacific with European/Other in males and females aged 1–74 years in New Zealand

Mentions: Ethnic inequalities in total cancer incidence varied substantially from the 1981–84 to the 2006–11 cohort. Trends in cancer incidence by ethnicity are shown in Fig. 4, and trends in cancer incidence SRDs in Fig. 5 (with data for endometrial, liver and cervical cancer, not available for mortality trends due to small numbers). The overall cancer incidence gap decreased for: Pacific males (53.6 to −77.6, p = 0.02) and probably also so for Māori males (37.8 to 25.3, p = 0.24) and Pacific females (19.2 to −9.6, p = 0.33). But in Māori females the gap appeared to increase (50.0 to 75.2 per 100 000, p = 0.22).Fig. 4


Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up
Decomposition of absolute ethnic inequalities in cancer incidence by major contributing cancer types, comparing Māori and Pacific with European/Other in males and females aged 1–74 years in New Zealand
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5037611&req=5

Fig5: Decomposition of absolute ethnic inequalities in cancer incidence by major contributing cancer types, comparing Māori and Pacific with European/Other in males and females aged 1–74 years in New Zealand
Mentions: Ethnic inequalities in total cancer incidence varied substantially from the 1981–84 to the 2006–11 cohort. Trends in cancer incidence by ethnicity are shown in Fig. 4, and trends in cancer incidence SRDs in Fig. 5 (with data for endometrial, liver and cervical cancer, not available for mortality trends due to small numbers). The overall cancer incidence gap decreased for: Pacific males (53.6 to −77.6, p = 0.02) and probably also so for Māori males (37.8 to 25.3, p = 0.24) and Pacific females (19.2 to −9.6, p = 0.33). But in Māori females the gap appeared to increase (50.0 to 75.2 per 100 000, p = 0.22).Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Background: Cancer makes up a large and increasing proportion of excess mortality for indigenous, marginalised and socioeconomically deprived populations, and much of this inequality is preventable. This study aimed to determine which cancers give rise to changing ethnic inequalities over time.

Methods: New Zealand census data from 1981, 1986, 1991, 1996, 2001, and 2006, were all probabilistically linked to three to five subsequent years of mortality (68 million person-years) and cancer registrations (87 million person years) and weighted for linkage bias. Age-standardised rate differences (SRDs) for Māori (indigenous) and Pacific peoples, each compared to European/Other, were decomposed by cancer type.

Results: The absolute size and percentage of the cancer contribution to excess mortality increased from 1981–86 to 2006–11 in Māori males (SRD 72.5 to 102.0 per 100,000) and females (SRD 72.2 to 109.4), and Pacific females (SRD −9.8 to 42.2) each compared to European/Other.

Results: Specifically, excess mortality (SRDs) increased for breast cancer in Māori females (linear trend p < 0.01) and prostate (p < 0.01) and colorectal cancers (p < 0.01) in Māori males. The incidence gap (SRDs) increased for breast (Māori and Pacific females p < 0.01), endometrial (Pacific females p < 0.01) and liver cancers (Māori males p = 0.04), and for cervical cancer it decreased (Māori females p = 0.03). The colorectal cancer incidence gap which formerly favoured Māori, decreased for Māori males and females (p < 0.01).

Results: The greatest contributors to absolute inequalities (SRDs) in mortality in 2006–11 were lung cancer (Māori males 50 %, Māori females 44 %, Pacific males 81 %), breast cancer (Māori females 18 %, Pacific females 23 %) and stomach cancers (Māori males 9 %, Pacific males 16 %, Pacific females 20 %). The top contributors to the ethnic gap in cancer incidence were lung, breast, stomach, endometrial and liver cancer.

Conclusions: A transition is occurring in what diseases contribute to inequalities. The increasing excess incidence and mortality rates in several obesity- and health care access-related cancers provide a sentinel warning of the emerging drivers of ethnic inequalities. Action to further address inequalities in cancer burden needs to be multi-pronged with attention to enhanced control of tobacco, obesity, and carcinogenic infectious agents, and focus on addressing access to effective screening and quality health care.

Electronic supplementary material: The online version of this article (doi:10.1186/s12885-016-2781-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus